PARIS - Salty water just below the surface of Mars could hold enough oxygen to support the kind of microbial life that emerged and flourished on Earth billions of years ago, researchers reported Monday (Oct 22).
In some locations, the amount of oxygen available could even keep alive a primitive, multicellular animal such as a sponge, they reported in the journal Nature Geosciences.
"We discovered that brines" - water with high concentrations of salt - "on Mars can contain enough oxygen for microbes to breathe," said lead author Vlada Stamenkovic, a theoretical physicist at the Jet Propulsion Laboratory in California.
"This fully revolutionises our understanding of the potential for life on Mars, today and in the past," he told AFP.
Up to now, it had been assumed that the trace amounts of oxygen on Mars were insufficient to sustain even microbial life.
"We never thought that oxygen could play a role for life on Mars due to its rarity in the atmosphere, about 0.14 per cent," Stamenkovic said.
By comparison, the life-giving gas makes up 21 per cent of the air we breathe.
On Earth, aerobic - that is, oxygen breathing - life forms evolved together with photosynthesis, which converts CO2 into O2. The gas played a critical role in the emergence of complex life, notable after the so-called Great Oxygenation Event some 2.35 billion years ago.
But our planet also harbours microbes - at the bottom of the ocean, in boiling hot springs - that subsist in environments deprived of oxygen.
"That's why - whenever we thought of life on Mars - we studied the potential for anaerobic life," Stamenkovic.
LIFE ON MARS?
The new study began with the discovery by Nasa's Curiosity Mars rover of manganese oxides, which are chemical compounds that can only be produced with a lot of oxygen.
Curiosity, along with Mars orbiters, also established the presence of brine deposits, with notable variations in the elements they contained.
A high salt content allows for water to remain liquid - a necessary condition for oxygen to be dissolved - at much lower temperatures, making brines a happy place for microbes.
Depending on the region, season and time of day, temperatures on the Red Planet can vary between minus 195 and 20 deg C.
The researchers devised a first model to describe how oxygen dissolves in salty water at temperatures below freezing.
A second model estimated climate changes on Mars over the last 20 million years, and over the next 10 million years.
Taken together, the calculations showed which regions on the Red Planet are most likely to produce brine-based oxygen, data that could help determine the placement of future probes.
"Oxygen concentrations (on Mars) are orders of magnitude" - several hundred times - "greater than needed by aerobic, or oxygen-breathing - microbes," the study concluded.Baretraps Brown Maryjanes Sz.7M Slip On Flat Shoes MINT CONDITION$45 Crocs Womens Carlie Mary Jane Flower Flat Shoes, Cotton Candy/Fuchsia, US 7Keen Women's Mary Jane Suede Shoes Deep Robin's Egg Blue USA Women's Size 8MCole Haan Nantucket Camp Moc / Boat Shoe, #W05747, Navy Patent, Women's US 7.5 , NEW Rockport RocSports Lite Cross Leather Ballet Flats, Women's Size 7.5M, BoneLFL by Lust for Life Womens Sport Gold Leather Size 6.0 LQgsSteve Madden Womens 'P-Almo' Flat Shoe, Gold Glitter, US 6 , ecco Light Shock Point Womens Size 42 US 11 Bicycle Toe Brown Leather Pumps ShoeNew Clarks Bendables size 9.5 W Whistle Max brown loafers zipper boots 67665 , Rieker Women's Slip-ons Low Shoes Ballerina Pumps Black, l0559neu$145 VIA SPIGA KEEPER Camel SOFT Leather Designer Comfort Pumps 7 RUN SMALLSperry Top Sider SABRINA Coral Pink Leather Slip On Tassel Loafers Flats Womens , NEW Womens Sperry Gold Authentic Original Boat Shoes Brown Size 5 M , Ryka Women's Calina Loafer, Black/Yucca Mint/White, Size 8.5 AvP1Brooks Womens Size 10 Hyperion Black Athletic Running Training Shoes ZV-513 , Guess pink Women's Sneakers Shoes 5.5Womens MBT Chapa Heather Toning Shoes, Size 8 Gray/ blue " MISSING INSOLE PAD"RYKA Women's Faze Cross Trainer, Black/Gray, Size 11 Sneaker ShoeWomen's Frye Helena Suede Flat Easy-to-clean Surface Flats , Women's Ladies Spot On Shoes F9819 Environment-friendly Flats , Nike WMNS Free Transform Flyknit Running Shoes Trainers 833410 600 6.5New Womens Nike SF AF1 MID Special Forces Shoes Air Force 1 AA3966-002 sz 5.5 , Valentine's Day Special-Newfoundland Dog Print Running Shoes For Women-Free ShipNEW Converse All Star CTAS Hi Top Natural/Brake Light Womens Shoes Sz 8 551644F , Sperry Top-Sider Crest Knoll Fashion Sneakers 712, Grey, 5 US / 35 EUKeds Champion Metalic Canvas Sneakers Navy WF56438 Women Casual Shoes TrackingNike Free TR Flyknit 2 Womens Training Shoes 904658 400 Size 11 , New Balance Womens Black WW847BK2 Sneakers Size 10.5 Med , Marc Fisher Chessi Fashion Sneakers 930, Bronze Multi, 8 USSkechers Women Blue Go Step Lite Memory Foam Slip On Loafers size 9 ,
"Our results do not imply that there is life on Mars," Stamenkovic cautioned. "But they show that the Martian habitability is affected by the potential of dissolved oxygen."